The present invention relates to a magnetic disk drive that uses a magnetoresistive head, and more particularly to a method of setting the amount of power application to a heater for controlling the magnetoresistive head flying height.
In recent years, the magnetic recording density provided by a magnetic disk drive has remarkably increased. It is mainly due to an extreme reduction in the magnetic head flying height, that is, the gap between a magnetic recording medium and magnetic head in the magnetic disk drive, which relates to a major technology for magnetic recording density increase. However, when the flying height decreases, the probability with which the medium strikes against the magnetic head increases, thereby giving rise to various problems including thermal asperity occurrence, head output attenuation, and head noise increase. Under these circumstances, a new technology is proposed for use with the magnetic head and magnetic disk drive. This technology controls the gap between the medium and magnetic head to such an extent as to avoid the above problems and decreases the gap only when a signal is to be written onto the medium or a medium signal is to be read.
An inductive magnetic head and magnetic disk drive disclosed, for instance, by Patent Document 1 (Japanese Patent Laid-Open No. Hei 5-20635) are such that a thin-film resistor (heater) is embedded in the magnetic head and heated to vary the flying height. A magnetoresistive head and magnetic disk drive disclosed, for instance, by Patent Document 2 (Japanese Patent Laid-Open No. 2003-272335) are such that a signal write section is separate from a signal read section while a heater is incorporated to control the gap between a magnetic recording medium and the magnetic head. A magnetic head slider and magnetic disk drive disclosed, for instance, by Patent Document 3 (Japanese Patent Laid-Open No. 2004-241092) are such that a heater is positioned so as to avoid a temperature rise in a magnetoresistive element and used to control the flying height.
For exercising control to optimize the power application amount for heating the thin-film resistor, the above conventional technologies detect contact between the head and medium, detect the head output level, bring the head into point contact or line contact with the medium, or detect the head ambient temperature and convert it to flying height information.